TF卡不能检卡问题排查

bring up阶段SD始终不能检卡，我觉得软件配置应该没问题，硬件是外包的，硬件答复这套设计其他厂商也在用没问题。SD一个卡槽，SIM一个卡槽，高通平台，Linux内核版本3.18。

先看下内核文档关于检卡的描述：

Card detection:
If no property below is supplied, host native card detect is used.
Only one of the properties in this section should be supplied:

• broken-cd: There is no card detection available; polling must be used.
• cd-gpios: Specify GPIOs for card detection, see gpio binding
• non-removable: non-removable slot (like eMMC); assume always present.

再看下dts配置:

&sdhc_2 {
         #address-cells = <0>;
        interrupt-parent = <&sdhc_2>;
        interrupts = <0 1 2>;
        #interrupt-cells = <1>;
        interrupt-map-mask = <0xffffffff>;
        interrupt-map = <0 &intc 0 125 0
                        1 &intc 0 221 0
                        2 &msm_gpio 38 0>;
        interrupt-names = "hc_irq", "pwr_irq", "status_irq";
        cd-gpios = <&msm_gpio 38 0x1>; //0x1 - 表示插卡低有效

这里用的就是gpio中断检卡方式不能工作，解析cd-gpios在sdhci_msm_populate_pdata：

enum of_gpio_flags flags = OF_GPIO_ACTIVE_LOW; //is 1

...   

pdata->status_gpio = of_get_named_gpio_flags(np, "cd-gpios", 0, &flags);
if (gpio_is_valid(pdata->status_gpio) & !(flags & OF_GPIO_ACTIVE_LOW))
        pdata->caps2 |= MMC_CAP2_CD_ACTIVE_HIGH;

把cd-gpios去掉就是用host native方式插拔检测正常，这种是轮训方式，sdhci_add_host里有：

/*   
 * Enable polling on when card detection is broken and no card detect
 * gpio is present.
 */
if ((host->quirks & SDHCI_QUIRK_BROKEN_CARD_DETECTION) &&
    !(mmc->caps & MMC_CAP_NONREMOVABLE) &&
    (mmc_gpio_get_cd(host->mmc) < 0) &&
    !(mmc->caps2 & MMC_CAP2_NONHOTPLUG))
        mmc->caps |= MMC_CAP_NEEDS_POLL;

为什么用gpio中断方式不能检测呢，来看下：

中断注册在mmc_gpiod_request_cd_irq：

void mmc_gpiod_request_cd_irq(struct mmc_host *host)
{
        struct mmc_gpio *ctx = host->slot.handler_priv;
        int ret, irq;

        if (host->slot.cd_irq >= 0 || !ctx || !ctx->cd_gpio)
                return;

        irq = gpiod_to_irq(ctx->cd_gpio);

        /*  
         * Even if gpiod_to_irq() returns a valid IRQ number, the platform might
         * still prefer to poll, e.g., because that IRQ number is already used
         * by another unit and cannot be shared.
         */
        if (irq >= 0 && host->caps & MMC_CAP_NEEDS_POLL)
                irq = -EINVAL;

        if (irq >= 0) {
                ret = devm_request_threaded_irq(&host->class_dev, irq,
                        NULL, mmc_gpio_cd_irqt,
                        IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
                        ctx->cd_label, host);
                if (ret < 0)
                        irq = ret;
        }   

        host->slot.cd_irq = irq;

        if (irq < 0)
                host->caps |= MMC_CAP_NEEDS_POLL;
}

中断处理是mmc_gpio_cd_irqt：

static irqreturn_t mmc_gpio_cd_irqt(int irq, void *dev_id)
{
        /* Schedule a card detection after a debounce timeout */
        struct mmc_host *host = dev_id;

        host->trigger_card_event = true;
        mmc_detect_change(host, msecs_to_jiffies(200));

        return IRQ_HANDLED;
}

mmc_detect_change会callmmc_schedule_delayed_work(&host->detect, delay);,也就是会走mmc_rescan，因为前面有挂INIT_DELAYED_WORK(&host->detect, mmc_rescan); 。

sdhci_request里检卡：

/*   
 * Firstly check card presence from cd-gpio.  The return could
 * be one of the following possibilities:
 *     negative: cd-gpio is not available
 *     zero: cd-gpio is used, and card is removed
 *     one: cd-gpio is used, and card is present
 */
present = mmc_gpio_get_cd(host->mmc);
if (present < 0) { 
        /* If polling, assume that the card is always present. */
        if (host->quirks & SDHCI_QUIRK_BROKEN_CARD_DETECTION)
                present = 1; 
        else 
                present = sdhci_readl(host, SDHCI_PRESENT_STATE) &
                                SDHCI_CARD_PRESENT;
}    

注释写的很清楚，先看cd-gpio情况。

把mmc_gpio_get_cd加入中断处理mmc_gpio_cd_irqt中查看发现插卡时有太多的中断打印，拔出停止。

中断频繁可以看到142一直在增：

msmxxx:/ # cat /proc/interrupts  | grep msmgpio
117:         11          1          1          2   msmgpio  13  msg2xxx
125:          0          0          0          0   msmgpio  21  cs35l41
142:      10651       1639        499          0   msmgpio  38  7864900.sdhci cd

GPIO配置确认：

msmxxx:/ # cat /sys/kernel/debug/gpio | grep 38
 gpio38  : in  0 2mA no pull

当修改为高有效后插入中断一个，拔出中断多出几个，但是仍然不能检卡，插卡mmc_gpio_get_cd返回0，拔卡返回1。之前其他项目配置高有效时，插卡get_cd返回的都是1，拔卡返回的是0，所以应该是硬件问题，push硬件修改后果然正常了。

这类情况以前在Z就遇到过，so有时不想调dd：]